Conversion of naphthas to middle distillates



July 28, 1964 c. N. KIMBERLIN, JR., ETAL 3,142,533

CONVERSION oF NAPHTHAS To MIDDLE nIsTILLATEs Filed Aug. 18. 1959 m 3 T N E V m oom Q2 m n wn r. J n.. .M om( l mommm zommom m m m n M T k .umm n wm nE NN 0 e nr w wm .J mm vm N d .m v. m m m w @N .J mEbS C um um -Jmo.zo ..5 m..

BY Mt/. 07%( PATENT ATTORNEY Unted States Patent O 3,142,633 CONVERSION F NAPHTHAS T0 MIDDLE DISTILLATES Charles Newton Kimberlin, Jr., Henry George Ellert, and

Howard Emerson Merrill, Baton Rouge, La., assignors to Esso Research and Engineering Company, a corporation of Delaware Filed Aug. 18, 1959, Ser. No. 834,455 6 Claims. (Cl. 20S-46) The present invention relates to distillate fuel manufacture` and it pertains more specifically to the manufacture of high quality distillate fuels such as heating oils, diesel fuel, jet fuels and the like from naphthas boiling in the gasoline boiling range.

The principal object of the present invention is to provide a process for converting low octane and/or unstable naphthas into materials of higher value and higher boiling range.

Hitherto, oil refineries have been generally operated to maximize naphtha production for use as gasoline motor fuel. Some naphthas are of substantially lower octane value than others, but could be blended with high anti-knock constituents to produce gasoline blends of acceptable quality. However, with the introduction of high compression ratio automobile engines, the octane requirements of gasoline have been steadily increasing, thus severely narrowing the choice of constituents suitable as gasoline blending agents. Thus, much virgin naphtha and naphthas resulting from catalytic cracking of gas oil, hitherto used as gasoline blends for engines of moderate compression ratio, can no longer be used for this purpose. Similarly, refinery processes such as uidized coking of residua, and visbreaking operations produce naphthas that are unstable and sludge forming, and are of too high sulfur content for satisfactory use as fuels.

Concomitant with the increasing accumulation of these relatively low value naphthas in the refineries, there has grown up in recent years substantial demands for hydrocarbons boiling in the middle distillate range of about 300 to 750 F. The rapid growth of heating oil installations both here and abroad, and the rapid dieselization of transportation equipment has caused the supply of middle distillates to be out of balance with that of motor gasolines. However, operating crude oil and distillate refinery processes to maximize middle distillates would seriously interfere with the production of high quality naphthas. An object of the present invention is to provide middle distillate fuels without interfering with maximum high quality and octane gasoline production.

Thus, heretofore middle distillate fuels have been produced as by-products in the manufacture of gasoline, and such fuels of relatively high quality could be obtained directly from fractions of the virgin crude oil or from the cracking of virgin crudes. The phenomenal increase in demand for middle distillate fuels has presented a serious problem to the oil refining industry.

Middle distillates, or distillate fuels, generally boil in the range of about 350 to 750 F., the so-called heater oils boiling in the range of 350 to 550 F., While diesel fuels boil at about 400 to 650 F.

In accordance with the present invention, refinery imbalance between gasoline and heating oil demands and stocks are restored by catalytic conversion of low quality naphtha fractions into middle distillates. In a sense this is the reverse of the hitherto trend of petroleum refining where the gasoline fraction was the desired product, and where low grade gasoline fractions were upgraded to high anti-knock material by such processes as reforming or isomerization.

The present invention involves principally conversion ICC of naphtha into middle distillate by catalytic treatment with liquid hydrogen fluoride and in the further presence, if desired, of certain promoters such as boron iiuoride or other halide, iron fluoride, and similar compositions. In one embodiment of the present invention, light virgin naphtha is directly converted. In another embodiment, naphtha may be thermally, catalytically or steam cracked to a relatively low degree of conversion, forming substantial quantities of olefins which are then passed to the catalytic conversion zone. In still another embodiment, low grade catalytic or Coker naphtha is fed directly into the conversion Zone, or is mixed with virgin or casinghead naphtha prior to conversion.

The catalyst employed in the present invention is anhydrous liquid HF. This may, particularly when virgin naphthas are being reacted, be augmented with BF3. In this case from 0 to 60 mol percent, preferably, 25 to 40 mol percent BFS based on HF, may be employed. Lesser amounts of from 0 to 10 mol percent, but preferably, 0 to 2 mol percent BF3 may be employed in processing the more reactive catalytic and coker naphthas or other naphthas containing oleiins.

Several critical conditions must be maintained in accordance with the present invention to obtain good yields of middle distillates. Temperatures must be in the range such that middle distillates rather than lubricating oil range material on the one hand, or products boiling lower than middle distillates on the other, are formed. In general, temperatures should be in the range of from about 0 to 350 F., preferably, 32 to 250 F. Process temperature is determined by the nature of the feed, the catalyst composition and the catalyst concentration. Normally, temperatures in the range of to 250 F., preferably, to 225 F. are employed in processing virgin naphthas using HF-BF3 catalyst, While lower temperatures in the range of 25 to 150 F., preferably, 75 to 125 F. give satisfactory results in processing catalytic or coker naphthas or other unsaturated feeds. Pressures are such that at least a portion of the catalyst and the feed are maintained in the liquid phase. Catalyst to oil ratios are in the range of 0.1 to 5/ 1, and preferably 0.5 to f2.5/ 1, and contact times to 5 to 180 minutes are maintained. Again, these conditions will be determined by the reactivity of the naphtha feed, high catalyst to oil ratios and long contact times being required with virgin naphthas with low catalyst to oil ratios and short contact times being satisfactory for the conversion of catalytic or coker naphthas. Specifically, catalyst to oil ratios of l to 5/ 1, preferably 2 to 4/ 1, and contact times of 30 to 180 minutes, generally 30 to 120 minutes, are employed in processing virgin naphthas. For catalytic and coker naphthas, catalyst to oil ratios of 0.1 to 1.5/1 and contact times of 5 to 30 minutes are normally satisfactory.

An important problem arising out of the reaction and reaction conditions heretofore described is the formation of secondary reaction products, and in particular the formation of dry gases, principally propane and isobutane, decreasing the ultimate yield of desired product. It has been found that the yield of desired middle distillates can be increased by passing these light products back to the reaction zone where either through mass action effects or through their reaction with the catalyst system present, they are converted into middle distillate. Suprisingly, however, it has been found that if a portion of the desired middle distillate product itself is recycled, on the order of 2 to 40% based on feed, the formation of the light material is greatly reduced.

The objects of the invention and its advantages will be more readily apparent from the more detailed description hereinafter when read in conjunction with the accompanying drawing showing a preferred embodiment thereof.

Turning now to the figure, a naphtha feed comprising low octane quality constituents, such as virgin naphtha, is admitted through inlet 10, pump i2 and valve 14 into mixer 16. Preferably, prior to admission to 16, the hydrocarbon stream is admixed with concentrated, and preferably anhydrous liquid HF admitted through line 18 and valve 20. The proportion of hydrouoric acid is preferably in the range of 2 to 4 times by weight of the total hydrocarbon fluids. Mixing ofthe acid and hydrocarbons may be effected by any one of a number of methods, as by use of special mixers or emulsitiers or by maintaining high linear velocities in the lines.

Preferably, prior to addition of the acid to the hydrocarbon, boron liuoride is added to the former to the extent of to 40 mol percent. In general, if the hydrocarbon feed is moderately or highly oleiinic, EP3 may be omitted, whereas its presence is beneiicial and indeed essential when the hydrocarbon feed is low in olen content, as is the case in virgin naphtha.

The resulting mixture of acid, BF3 and hydrocarbon is passed to heater 22 wherein it is heated to suitable reaction temperatures of the order of 175 to 225 F., and passed to reaction chamber 24, wherein it is maintained for a period of to 120 minutes at a pressure suicient to maintain major portions of the catalyst and feed in the liquid phase. Agitation by any known means may be supplied, as by recirculation.

Effluent mixture from reactor 24 is passed through conduit 26 to separator 30 wherein it is separated into two liquid phases as by cooling and gravitation or centrifugal means. The heavier or HF-BF3 acid phase may be recycled via conduit 32 to pump 34; a portion may continuously be passed to an acid fractionator (not shown) or other means for purifying and restoring the acid, all in a manner known per se.

Returning to the upper layer, the hydrocarbon phase is passed through line 36 to tractionator 38, preferably with pressure release. In accordance with the present invention, the light products, such as the butanes and propane, are recycled to reactor 24 via line 40. Similarly, from 2 to 60% by weight of the desired middle distillate, and which fraction boils between about 250 and 650 F., is recycled via line 42 to reactor 24, while unreacted hydrocarbon naphtha may similarly be recycled via line 44. The middle distillate fraction is passed via line 46 to a finishing plant or for further treatment not forming a part of this invention.

The process of the present invention is further illustrated by the following speciiic examples,

Example I A virgin naphtha obtained from a South Louisiana crude and boiling from 215 to 350 F. was treated according to the method outline above. Experimental conditions were:

HF/oil wt. ratio 2 BPB/oil wt. ratio 0.4 Temperature, F Contact time, hrs 2 The reactor was a Monel autoclave equipped with an eicient agitator. The developed pressure was held through the treat. At these conditions the naphtha conversion was 71.6 wt. percent and the wt. percent yields, based on naphtha converted were:

C3- 5.6 C.l 39.5 C5 15.4 o/65o F 395 Example II A light catalytic naphtha obtained by cracking a South Louisiana crude and boiling from 165 to 350 F. Was

treated in a stirred Monel autoclave under the following conditions:

HF/oil wt. ratio 0.2 Temperature, F 150 Contact time, hrs 0.5

No BF3 was used. At these conditions 55.3 wt. percent conversion of the naphtha was obtained. The wt. percent yields based on converted naphtha were:

C3- C., 0.9 350/650 F 98 9 Example III [225 F., 2 HF/hydrocarbon wt. ratio, 20 wt. percent BFa on HF, 2 hr. reaction time] Feed Composition:

Naphtha Isobutane 5.2507650c F Naphtba Converted to Wt. percent Yields, Wt. percent on Naphtha Converted to C3 and 250 F. -l-z Ca- 250/650 F It is evident from the above data that middle distillate production is maximized and gas make minimized by recycling at least a portion of the butane or C4* and 250 E+ product fractions with unconverted feed.

What is claimed is:

l. An improved process for converting naphthas to hydrocarbons boiling in the middle distillate range of from about 250 to about 650 F. which comprises treating said naphtha in a reaction zone in the liquid phase with anhydrous hydrofluoric acid at a temperature in the range of about 0 to about 350 F., whereby a substantial amount of said naphtha is converted to middle distillates and light hydrocarbons, segregating the product from said reaction zone into light hydrocarbons and middle distillates, and recycling light hydrocarbons, consisting essentially of propane and butanes, and a significant portion of said middle distillates to said reaction zone.

2. An improved process for converting naphthas to hydrocarbons boiling in the middle distillate range of from about 250 to about 650 F. which comprises treating said naphtha in a reaction zone in the liquid phase with anhydrous hydrouoric acid at a temperature in the range of about 0 to about 350 F., whereby said naphtha is converted to middle distillates boiling in the range of about Z50-650 F. and light hydrocarbons, consisting essentially of propane and butanes, segregating the product from the reaction zone into light hydrocarbons and middle distillates, and recycling said light hydrocarbons, and about 2 to 60 percent based on feed of the middle distillate product to said reaction zone.

3. An improved process for converting naphthas boiling in the range of about 16S-350 F. into middle distillates which comprises treating said naphtha in a reaction zone in the liquid phase with anhydrous hydrofluoric acid at a temperature in the range of about 32 to 450 F., maintaining the reactants in a catalyst to oil ratio of 0.1-5/1 and at a Contact time of 5 to 180 minutes whereby said naphtha is converted to middle distillates boiling in the range of about Z50-650 F. and light hydrocarbons, consisting essentially of propane and butanes, segregating the hydrocarbon product from the reaction zone into light hydrocarbons and middle distillate and recycling said light contains olenic hydrocarbons and to 10% BFS, based hydrocarbons and from about 2-60 percent based on feed on HF, is added to said zone, said temperature being in of said middle distillate product to the reaction zone. the range of about 25 to 150 F.

4. The process of claim 3 wherein 0 to 60 mol percent BF3, based on HF, is added to said reaction Zone. 5 References Cited m the me of this Patent 5. The process of claim 1 wherein said naphtha feed UNITED STATES PATENTS hydrocarbon is substantially paranicand about` to 2,445,560 Caldwell July 2()l 1948 BFS, based on HF, 1s added to said zone, said tern- 2,463,372 Heim-ich Man 3, 1949 perature being in the range of from about to about 2,684,325 Deanesly July 20J 1954 250 F. 10 2,927,072 Gladrow et al. Mar. 1, 1960 6. The process of claim 1 wherein said naphtha feed 2,938,855 Mason et al. May 31, 1960 

1. AN IMPROVED PROCESS FOR CONVERTING NAPHTHAS TO HYDROCARBONS BOILING IN THE MIDDLE DISTILLATE RANGE OF FROM ABOUT 250 TO ABOUT 650*F. WHICH COMPRISES TREATING SAID NAPHTHA IN A REACTION ZONE IN THE LIQUID PHASE WITH ANHYDROUS HYDROFLUORIC ACID AT A TEMPERATURE IN THE RANGE OF ABOUT 0 TO ABOUT 350*F., WHEREBY A SUBSTANTIAL AMOUNT OF SAID NAPHTHA IS CONVERTED TO MIDDLE DISTILLATES AND LIGHT HYDROCARBONS, SEGREGATING THE PRODUCT FROM SAID REACTION ZONE INTO LIGHT HYDROCARBONS AND MIDDLE DISTILLATES, AND RECYCLING LIGHT HYDROCARBONS, CONSISTING ESSENTIALLY OF PROPANE AND BUTANES, AND A SIGNIFICANT PORTION OF SAID MIDDLE DISTILLATES TO SAID REACTION ZONE. 